2.2 Quiz

Lewis Structures:

• if it’s a halogen, with 7 valence electrons, it can only form one bond

• if it has 6 valence electrons, it can form a double bond

• if it has 5 valence electrons it can form a triple bond

• if it has 4 valence electrons it can form a triple bond as well

• the atom has to be responsible for as many indivisual electrons as there are valence electrons

• sulfur and phosphorus are exceptions because they can surpass the octet rule; this is because they have empty d orbitals that can be filled with extra electrons, giving rise to the possibility of an expanded octet

Formal charge:

• Valence electrons-electrons in lone pairs-# of bonds

• the goal is for the formal charge to be zero on most of the atoms

• each charge adds to the overall charge

Resonance structures:

• molecular compounds with more than 1 possible lewis structure

VSEPR Shapes

• linear if there are 2 atoms bonded to the central atom and zero lone pairs

  • 180 degrees

• linear if there are only 2 atoms; can’t make a shape

  • 180 degrees

• bent if there are 2 atoms bonded to the central atom and one lone pair

  • a little <109.5 degrees

• bent if there are 2 atoms bonded to the central atom and 2 lone pairs

  • a little <109.5 degrees

• trigonal planar if there are 3 atoms bonded to the central atom and 0 lone pairs

  • 120 degrees

• trigonal pyramidal if there are 3 atoms bonded to the central atom and 1 lone pair

  • a little <109.5 degrees

• tetrahedral if there are 4 atoms bonded to the central atom and 0 lone pairs

  • 109.5 degrees

Electronegativity and Intermolecular Forces

• types of bonds

  • london dispersion, in all molecules

  • dipole-dipole, in polar molecules

  • hydrogen bonding in polar molecules with H-F, H-O, H-N bonds

• compound is nonpolar if

  • the central atom has 0 lone pairs

  • all atoms around central atom are the same

• dipole moments point toward the most electronegative molecules

  • bond polarity is toward the more electronative atom

  • molecular polarity is the overall dipole moment

• pauling scale

  • If the electronegativity is

    • <0.4, nonpolar

    • 0.4-1.7, polar

    • >1.7, ionic